Behavior of Y ersinia enterocolitica in UF White Cheese: Impact of Different Storage Temperatures on Various Strains

Abstract

This study aimed to investigate the effect of different temperatures on survival of various strains of Yersinia enterocolitica during the storage of ultra-filtered (UF) white cheese. UF pasteurized cow milk was inoculated with 3 log colony-forming unit per gram of two standard strains (DSM 11502 and DSM 9499) and one native strain of Y. enterocolitica. Cheese samples were prepared according to the regular procedure and stored at 14, 8 and 25C. The variation of Y. enterocolitica populations was tracked throughout the 60 days of storage, and the enumerated colonies were confirmed by polymerase chain reaction. According to the results, the number of Y. enterocolitica increased significantly (P < 0.01) after incubation time; however, it was diminished during storage period. Data also suggested that survival of Y. enterocolitica is temperature dependent. Moreover, the native strain of Y. enterocolitica survived longer than standard strains. Practical Applications Rapid increasing of Y. enterocolitica during ultra-filtered (UF) white cheese preparation revealed the necessity for retaining hygienic conditions to avoid cross-contamination. In addition, the detrimental condition provided by the activity of starter bacteria, acidic pH, salt and storage time was not sufficient as Y. enterocolitica survived the 2-month storage period of UF white cheese. Results showed that behavior of native strains could be significantly different from the laboratory-adopted strains. Therefore, in food model studies it is recommended that the survival of native microbial strains be assessed along with the standard ones.